Some navigation apparatuses use map matching (see Japanese Patent Application Laid-Open No. H7-63570) whereby the current location is identified by finding the detected current position in a map showing the roads located within the travelable range for the purpose of calculating and displaying a planned travel route from the current location to the destination and, when the distance from the current location to the next branch point becomes equal to a predetermine distance, notifying the user of the distance thereto and the direction in which to travel with voice.
Nowadays, commercially available are not only navigation apparatuses dedicated to car-mounted use but also portable navigation apparatuses that can also be used by walkers. These navigation apparatuses, when mounted on a car, can perform map matching to guide along a travel route. However, when they are used by a walker, since the traveling speed is low relative to the precision of the GPS, it is difficult to calculate the traveling direction, and this makes it impossible to perform map matching correctly. To overcome this inconvenience, i.e., to permit map matching only when a navigation apparatus is mounted on a car and not when used by a walker, the applicant of the present invention once disclosed, in Japanese Patent Application Laid-Open No. 2000-18960, a navigation apparatus wherein whether an external power source or an internal power source is used is detected so that, when an external power source is used, map matching is permitted and, when an internal power source is used, map matching is not permitted.
However, according to the method disclosed in Japanese Patent Application Laid-Open No. 2000-18960 mentioned above, in a case where the navigation apparatus needs to be frequently mounted on and dismounted from a car, as in a case where parcels are delivered to addressees in a town, in which case the deliveryman needs, repeatedly for each destination, to travel by car to a nearby parking lot and then walk on foot therefrom to the destination, the navigation apparatus needs to be connected to and disconnected from an external power source every time it is mounted on and dismounted from the car.
Moreover, in a case where the mode of traveling is changed, as from traveling by car to traveling on foot, or from traveling by four-wheeled car to traveling by motor bicycle, it is necessary to change the settings of the sound volume level, the distance to the next branch point at which to give a guidance, and the like one by one to best suit the given mode of traveling every time the mode of traveling is changed. This makes using the navigation apparatus troublesome.